LLC谐振变换器的研究与性能优化

发布时间：2018-02-27 03:17

本文关键词： LLC谐振变换器稳态建模小信号特性数字控制器设计 ZVS条件优化　出处：《华中科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：随着电力电子理论以及功率器件技术的发展，高频化成为电力电子变换器的必然趋势。开关频率的提高能够显著减小电路中磁性元件的体积，从而提高功率密度，但是随着而来的是效率的降低。为解决这一问题，软开关技术受到关注。谐振变换器即是一类利用电感、电容在每个开关周期中电流、电压周期性变化的特性，来实现开关管的软开通和软关断。本文首先介绍谐振变换器家族中几种常见拓扑的基本特性，针对本文的宽输出增益、宽负载变化的应用场合，选择LLC型拓扑来设计本文样机——10kW直流变换装置，接着介绍LLC的研究现状、关注热点，并给出本文所要研究的问题以及解决方案。 LLC多谐振变换器具有复杂的工作模态和多变的特性，为了更清晰的理解、描述这些状态，本文将LLC的工作状态首先分解为几个基本模态，然后以谐振频率为界，对不同频率区间、负载下的工作状态及其变化趋势作了详细的分析。然后，为了进一步分析和计算，首先建立基本模态的数学模型，然后给出组合模态的求解思路。 LLC谐振型直流变换器系统具有很强的非线性，导致控制上难以建立精确的模型。本文利用仿真来研究LLC谐振变换器的小信号特性。针对由2808DSP所构成的数字控制系统中调频调压精度以及数字延迟的问题，为了获得具备更好的稳定性及动态性能的系统，本文尝试使用高阶数字控制以及多变量反馈控制的策略，选取恰当的工作点，利用前面获得的LLC小信号特性，设计适用于整个工作范围内的控制器，，并以仿真验证。最后，对LLC的效率问题作了讨论，并对额定工作点处的效率作精确计算分析。考虑到实现ZVS条件对LLC优化运行的必要性，本文利用第二章所建立的模型，精确计算了能够实现主开关管ZVS的最小死区，并进一步讨论开关频率的范围。最后以仿真和实验验证了计算的准确性。
[Abstract]:With the development of power electronic technology and theory of power devices, high frequency power electronic converter has become an inevitable trend. The improvement of the switching frequency can decrease the magnetic element in the circuit volume, so as to improve the power density, but with the decrease of the efficiency. In order to solve this problem, soft switching technology has attracted more and more attention.
Resonant converter is a kind of the inductance, capacitance current in each switching cycle, voltage characteristics of cyclical changes, to achieve soft switching switch and soft switching. This paper firstly introduces several basic characteristics of common topology of resonant converter in the family, for the wide output gain, wide application load change in this paper, to design the prototype of 10kW DC converter LLC topology, and then introduces the research status of LLC, the focus, is given in this paper to study the problems and solutions.
Has the working mode of complex and volatile characteristics of LLC multi resonant converter, in order to more clearly understand, describe the state, the working state of LLC is first decomposed into several basic modes, and then taking the resonant frequency is bounded in different frequency range, working state and its change trend under load is analyzed in detail then, in order to further analysis and calculation, we first establish the mathematical model of basic mode, then the solution gives the combination mode.
LLC resonant DC-DC converter system with strong nonlinearity, leading to control it is difficult to establish an accurate model of small signal. To research the characteristics of LLC resonant converter is simulated by this paper. In view of the digital control system composed of 2808DSP frequency precision pressure regulator and digital delay problem, in order to obtain the system stability and dynamic performance better, this paper attempts to use the high order digital control and multi variable feedback control strategy, select the appropriate operating point, LLC small signal characteristics of the front of the controller design is suitable for the whole operating range, and by simulation.
Finally, the efficiency of LLC is discussed, and the efficiency of the rated working point for the accurate calculation and analysis. Considering the implementation of ZVS conditions on the necessity of running LLC optimization, the second chapter of the established model, the minimum dead zone to achieve the main switch ZVS is calculated accurately, and further discuss the scope switching frequency. Finally simulation and experimental results verify the accuracy of calculation.

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM46

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